A known production tractor uses three gear pumps in an open center hydraulic circuit with dedicated pumps for drivetrain lubrication, tractor implement hydraulics, and tractor steering and transmission control hydraulics. Other known production tractors have hydraulic circuits which include dedicated fixed displacement pumps for providing transmission lubrication and charge oil. A John Deere production tractor uses a priority valve to meter oil to the charge and lubrication circuit, but the excess oil must be returned to the sump or pump inlet. On other John Deere production tractors, a variable displacement charge pump provides oil to the inlet of the transmission pumps where the transmission pumps act as flow dividers to split oil to various pressure levels in the transmission lubrication circuit. These latter tractors have hydraulic systems which passively route a small volume of oil to minor lubrication consumers, but these consumers do not control the displacement of the variable displacement charge pump. Another John Deere production tractor has a hydraulic system in which a charge pump fills a clean oil reservoir from which the transmission pump suctions oil from an inlet to the reservoir. These hydraulic circuits require additional pump drives to move the oil to their desired locations which cost the tractor energy due to additional mechanical efficiency losses. Fixed displacement pumps produce excess flow at high engine speeds which must be either pumped through the circuit regardless of demand or bypassed back to tank. Tractor power is wasted when this extra volume of oil is moved without gaining any useful work from it. It is desired to provide a vehicle hydraulic circuit which is able to supply the required charge and lubrication flow with a single variable displacement pump.